This invention relates in general to ignition devices for explosive charges and in particular to a new and useful fuze for setting off jacketed explosive charges and to a method of regulating when the explosion takes place.
Military regulations concerning jacketed bursting charges require a separation of the main explosive charge from the priming charge. By priming charges such explosives are understood which are more sensitive than tetryl. This includes most of the detonators. Under these regulations, an explosive chain is permitted to close only after two unpriming conditions, independent of each other, are satisfied which cannot occur under other conditions of use. With spinning projectiles, such conditions may be the discharge acceleration and the rotation, for example.
With underwater explosive charges, such as sea mines or torpedo devices, considerable difficulties are met in attempts to find such criteria quite independent from each other. For example, it has been provided to employ a water soluble substance preventing the detonator from moving from safety to priming position as long as the substance has not dissolved in contact with water. The substance, however, was also sensitive to air humidity, so that an unintentional activation could not reliably be prevented. Further, the effect of such a mechanism cannot be reversed.
Frequently, however, it is desirable to render the underwater explosive charge safe again after it is removed from the water. A typical example are cable cutters used in mine sweeping. After hauling them in again, these cutting charges must be unprimed.
German Pat. No. 23 60 226 discloses a fuze for setting off jacketed explosive charges. That disclosure provides a mechanically driven device by which the hollow charge with its lining forming the breaking wall can be pivoted between an armed position in which the hollow firing charge is in alignment with the principal explosive charge, and a retracted position in which the intermediate safety space is formed between the two charges.
The mechanism needed for this purpose is relatively expensive. Further, priming is possible even with the charge out of water, and unpriming, after removing the charge from the water, again requires a pivoting of the hollow charge, i.e. an actuation of the pivoting mechanism.
From U.S. Pat. No. 3,190,219, there is known an arrangement with a device to be lowered into drill holes, comprising a blasting charge, a hollow charge lining, a liquid filled intermediate space between the blasting charge and the lining, and an empty further intermediate space provided in front of the lining in the effective direction of the charge. By the pressure wave produced upon the ignition of the blasting charge, a sharp fragment or spike is formed of the lining, piercing the drill pipe and penetrating into the adjacent ground. The liquid, such as water or hydrochloric acid, follows the spike and is intended to increase the depth of penetration and clean the passages underground.